1. Field of the Invention
The present invention relates to a method and apparatus for manufacturing semiconductor devices in which ruthenium films or ruthenium oxide films are formed on a substrate.
2. Description of the Related Art
For such a method of forming thin films of ruthenium or ruthenium oxide on a substrate, there has been known a typical example in which a ruthenium raw gas and a gas containing oxygen atoms such as, for example, oxygen (O2), ozone (O3), etc.) are reacted with each other in their vapor or gaseous phase inside a reaction chamber with a substrate received therein.
FIG. 5 is a view for explaining one example of a conventional semiconductor manufacturing apparatuses using such a method. The semiconductor manufacturing apparatus illustrated in FIG. 5 includes a reaction chamber 1, a container or vessel 2 containing a ruthenium liquid material, a vaporizer 3 for vaporizing the ruthenium liquid material, a ruthenium raw gas feed pipe 4 for feeding a vaporized ruthenium raw gas to the reaction chamber 1, an oxygen-containing gas feed pipe 5 for feeding an oxygen-containing gas such as, for example, a gas containing oxygen atoms (e.g., oxygen (O2), ozone (O3), etc.) to the reaction chamber 1, a gas mixing chamber 6, and a carrier gas pipe 11 and an exhaust pipe 22.
In the reaction chamber 1, there are provided a substrate holder 8 with an unillustrated heating source or heater for supporting a substrate 7 thereon, and a nozzle or shower head 9 for jetting or spraying a mixture of the ruthenium raw gas and the oxygen-containing gas containing oxygen atoms (e.g., oxygen (O2), ozone (O3), etc.) in a shower-like manner.
The gas mixing chamber 6 is arranged between the reaction chamber 1 and the ruthenium raw gas feed pipe 4, and between the reaction chamber 1 and the oxygen-containing gas feed pipe 5, and serves to mix the ruthenium raw gas and the oxygen-containing gas containing oxygen atoms (e.g., oxygen (O2), ozone (O3), etc.) with each other before these gases are supplied to the reaction chamber 1.
However, the conventional semiconductor manufacturing apparatus as described above has a deficiency in that it is extremely difficult to properly design of the shape or configuration of the gas mixing chamber 6. That is, in order to obtain a homogeneity or uniformity in the sheet resistance over the entire surface of the substrate, which is one of the characteristics required of semiconductor devices, it is necessary to configure the gas mixing space in the gas mixing chamber 6 into an optimal shape so as to permit the gases to easily mix with each other.
FIGS. 6(a) and 6(b) are views for explaining the shape of the gas mixing space in the gas mixing chamber 6. FIG. 6(a) is a side view of the gas mixing chamber 6, illustrating the interior thereof in broken lines. In FIG. 6(a), a diffuser 12 is arranged in the gas mixing chamber 6 so as to define gas mixing spaces 13 on the opposite sides thereof, i.e., on an upstream side and a downstream side thereof. FIG. 6(b) is a plan view of the diffuser 12. The diffuser 12 has a plurality of holes 14 formed therethrough, so that the gases introduced into the gas mixing chamber 6 from the ruthenium raw gas feed pipe 4 and the oxygen-containing gas feed pipe 5 pass through the holes 14, thereby being diffused to mix with each other.
It is necessary to re-set the optimal shape of the gas mixing spaces 13 each time the film-forming conditions such as the film-forming pressure, the flow rates of the gases, etc., are changed, and hence in the past, the optimal shape of the gas mixing spaces 13 is determined upon change of the film-forming conditions by performing simulations of the mixing of the gases, evaluations of actual models using a lot of trial shapes or prototypes, thus resulting in high costs.
Accordingly, the object of the present invention is to provide a semiconductor manufacturing method and apparatus which is capable of producing a semiconductor device having required characteristics, such as one with excellent uniformity in the sheet resistance over the entire surface of a substrate, without requiring a careful or elaborate determination of an optimal shape or configuration of a gas mixing chamber or without the use of such a gas mixing chamber.
Bearing the above object in mind, according to one aspect of the present invention, there is provided a semiconductor manufacturing method comprising: mixing a ruthenium raw gas vaporized from a ruthenium liquid material and a gas containing oxygen atoms in piping at a location upstream of a reaction chamber; and forming a ruthenium film or a ruthenium oxide film on a substrate by using a gas mixture of the ruthenium raw gas and the gas containing oxygen atoms mixed with each other in the piping.
With this semiconductor manufacturing method, it is possible to mix the vaporized ruthenium raw gas and the gas containing oxygen atoms with each other to a satisfactory extent without the need for a careful or deliberate determination of an optimal shape or configuration of a gas mixing chamber or without the use of such a gas mixing chamber itself.
In a preferred form of the semiconductor manufacturing method of the present invention, after the ruthenium raw gas and the gas containing oxygen atoms having been mixed with each other in the piping, both of the ruthenium raw gas and the gas containing oxygen atoms are further mixed with each other in a gas mixing chamber which is provided at a location between the reaction chamber and a mixing place in which the ruthenium raw gas and the gas containing oxygen atoms are mixed with each other in the piping.
Thus, both of the ruthenium raw gas and the gas containing oxygen atoms are further mixed with each other in the gas mixing chamber so that the vaporized ruthenium raw gas and the gas containing oxygen atoms can be mixed well to a more satisfactory extent.
According to another aspect of the present invention, there is provided a semiconductor manufacturing apparatus comprising: a reaction chamber in which a ruthenium film or a ruthenium oxide film is formed on a substrate; a vessel for accommodating therein a ruthenium liquid material; a vaporizer connected to the vessel for vaporizing the ruthenium liquid material to provide a ruthenium raw gas; a ruthenium raw gas feed pipe connected with the vaporizer and the reaction chamber for supplying the vaporized ruthenium raw gas to the reaction chamber; and an oxygen-containing gas feed pipe connected with the reaction chamber for supplying a gas containing oxygen atoms to the reaction chamber. The ruthenium raw gas feed pipe and the oxygen-containing gas feed pipe are merged with each other at a location upstream of the reaction chamber so that the ruthenium raw gas and the gas containing oxygen atoms are mixed with each other prior to being supplied to the reaction chamber.
With this arrangement of the semiconductor manufacturing apparatus, since the ruthenium raw gas and the gas containing oxygen atoms are mixed well prior to being supplied to the reaction chamber, it becomes possible to provide semiconductor devices with required properties such as, for example, excellent uniformity in the sheet resistance over the entire surface of a substrate, without using a gas mixing chamber. In addition, the nonuse of such a gas mixing chamber leads to a further reduction in cost. Moreover, it becomes possible to lower the partial pressure of the liquescent ruthenium raw gas, so that the ruthenium raw gas is prevented from being liquefied again in the course of flowing from the vaporizer to the reaction chamber, thus making it possible to a stable supply of the ruthenium raw gas.
In a preferred form of the semiconductor manufacturing apparatus of the present invention, a gas mixing chamber is provided between the reaction chamber and a merged portion of the ruthenium raw gas feed pipe and the oxygen-containing gas feed pipe for further mixing the ruthenium raw gas and the gas containing oxygen atoms which have been mixed with each other in the merged portion, prior to being supplied to the reaction chamber.
With such an arrangement, since the ruthenium raw gas and the gas containing oxygen atoms are mixed well prior to entering the gas mixing chamber, it becomes possible to provide semiconductor devices with required properties such as, for example, excellent uniformity in the sheet resistance over the entire surface of a substrate, without the need of carefully or deliberately determining an optimal configuration or shape of the gas mixing chamber. Thus, a careful or deliberate determination of an optimal configuration or shape of the gas mixing chamber becomes unnecessary, thereby contributing to a cost reduction. In addition, the simplified configuration of the gas mixing chamber serves to lower the partial pressure of the liquescent ruthenium raw gas, thereby preventing the ruthenium raw gas from being liquefied again in the course of flowing from the vaporizer to the reaction chamber. As a result, it is possible to supply the ruthenium raw gas to the reaction chamber in a stable manner.
The above and other objects, features and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention taken in conjunction with the accompanying drawings.